Obesity has reached epidemic proportions and represents a serious public health problem in the United States. Efforts to treat obesity have been only moderately successful, and attention has shifted toward prevention of weight gain, rather than treatment of obesity. Although average weight gain from pre- pregnancy to one-year postpartum is 2 kg, approximately 25 percent of women gain 5 kg or more during this period. Moreover, a recent study found that nearly 44 percent of normal weight women who had retained significant amounts of weight (M= 4.8 kg) at 12 months postpartum became overweight later in life. Thus, the period surrounding pregnancy appears to be an important time for prevention efforts. The single strongest predictor of weight gain from pre-to post-pregnancy is the magnitude of weight gained during pregnancy. The Institute of Medicine (IOM) has formulated specific recommendations for healthy weight gain during pregnancy. However, more than one-third of normal weight women and two thirds of overweight women exceed recommended levels of weight gain during pregnancy. Thus, helping women gain the recommended amount during pregnancy through healthy eating and physical activity would make a major contribution to preventing excessive weight retention. The principal aim of this study is to determine whether behavioral lifestyle intervention during pregnancy can reduce the number of normal weight and overweight women who exceed the IOM recommendations for weight gain during pregnancy. We propose to recruit 400 primiparous women and randomly assign these women to receive usual care or Intervention to Promote Healthy Weight Gain During Pregnancy. The Intervention group will receive weekly educational materials, weight monitoring with feedback, and supportive phone calls. All women will be followed from early pregnancy to 1-year postpartum. We believe this project is significant because it deals with the prevention of weight gain, which is a major health problem. The study is also innovative; there have been no adequately powered randomized controlled trials evaluating the effects of a behavioral lifestyle intervention delivered during pregnancy to promote healthy weight gain and prevent sustained postpartum weight retention. [unreadable] [unreadable] [unreadable]